            [com.google.javascript.jscomp
             CompilationLevel
             CompilerOptions
-            SourceFile]))
+            SourceFile
+            CompilerOptions$LanguageMode]))
 
 (defn- delete-target [target]
   (let [f (file target)]

        (com.google.javascript.jscomp.Compiler/setLoggingLevel Level/SEVERE))
      (let [assets   (aggregate path ".js")
            compiler (com.google.javascript.jscomp.Compiler.)
            result   (compile-js compiler assets externs optimization)]
        (with-open [wrt (writer target)]
          (.append wrt (.toSource compiler)))
        (merge result (compression-details assets (file target)))))))

      (.setOptionsForCompilationLevel options))
  options)

(defn- compile-js [compiler assets externs optimization language]
  (let [options  (-> (CompilerOptions.)
                     (doto (.setLanguage (-> language
                                             (name)
                                             (.toUpperCase)
                                             (CompilerOptions$LanguageMode/fromString))))
                     (doto (.setOutputCharset "UTF-8"))
                     (set-optimization optimization))]

